Measuring the distance between a woman’s anus and genitalia may help doctors determine whether she risks developing a serious form of endometriosis, according to a Spanish study.

Another finding was that women should avoid exposure to estrogen-like compounds in the environment because high levels of the female hormone in the uterus are associated with endometriosis. The disease is characterized by tissue that normally grows in the uterus growing outside it.

Since the distance between the anus and genitalia is determined by levels of male and female hormones during fetal development, the research also suggested that the foundations of endometriosis are laid down in the earliest stages of life.

The study, “Investigation of anogenital distance as a diagnostic tool in endometriosis,” was published in the journal Reproductive Biomedicine Online.

Researchers at the Virgen de la Arrixaca University Clinical Hospital examined 114 women with endometriosis and 105 controls to explore the theory that the uterus’ exposure to hormones is a risk factor for endometriosis.

Earlier research established that exposure to estrogen during fetal development leads to a shorter distance between the anus and genitalia, while exposure to male hormones leads to a longer distance.

While women with endometriosis were older than the controls — a mean age of 36.2 years versus 29.7 — and had more vaginal deliveries, other characteristics did not differ between the groups.

The team noted that a shorter distance was linked not only to endometriosis, but also to the endometriosis subgroups ovarian and deep-infiltrating endometriosis. The very shortest distances were seen in the 32 women with deep-infiltrating endometriosis.

Using a cut-off point of 20.9 mm, the team showed it was possible to discriminate between women with ovarian endometriosis and the infiltrating version. Only 22.4 percent of the combined group of  patients and controls had a shorter distance than 20.9 mm. But in the group with the infiltrating version of the disease, 84.4 percent had a distance below the cut-off.

Doctors should be able to use the measurement to predict a severe form of the disease in 84.4 percent of cases, and exclude a severe form with 91.4 percent accuracy.

Women produce estrogen while pregnant, but a fetus can obtain it not only from the mother but also from chemicals and substances in food — so-called xenoestrogens that mimic the actions of estrogen. Studies have shown that bisphenol A, found in many plastics; phytoestrogens, found in foods such as soy; and the chemical monobutyl phthalate also reduce the distance between the anus and genitals in newborn girls.

“Gynecologists may be able to evaluate with this anthropometric measurement the individual likelihood of patients to develop severe forms of clinical endometriosis before the patients develops serious symptoms or infertility problems,” the researchers wrote. “Our findings have additional public health implications as prevention of prenatal exposure to hormonal substances and endocrine disruptors should be a high priority.”